The focus of our research is the life cycles of temperate phage P2 and satellite phage P4, which depends upon P2 as a helper. We shall study the interactions of satellite and helper phage activators, as well as the P4 virulence suppression protein (Vis), with two sites in a P4 late gene promoter. An upstream site functions in positive activation, whereas a downstream site is needed for repression by satellite phage activators. The Vis protein may overcome this repression. One satellite phage activator, P4 Delta, has two standard activator domains lined covalently. We shall study the binding of Delta to the alpha subunit of RNA polymerase, as well as to DNA. The amino terminal domain of Delta may bind DNA, whereas the carboxyl-terminal domain may contact RAN polymerase. We shall determine how the P2 phage Tin gene produce interferes with the growth of phage T4. T4 mutations that overcome this interference are in the essential single stranded DNA binding protein, gp32. We shall overproduce and purify the tin protein and determine whether it is a single stranded DNA binding protein that competes with gp32. If this turns out to be true, we shall mutate amino acid residues of Tin that are part of a putative single stranded DNA binding motif, in order to see whether these amino acids are essential for interference, as well as DNA binding. We shall study the mechanism by which the P4 phage polarity suppression protein (Psu) causes transcription antitermination at Rho- dependent termination sites. We shall determine whether Rho is permanently inactivated by Psu, and if Rho is inactivated, we shall determine the means by which inactivation occurs. This project is health-related in that it explores fundamental processes of virus life cycles in a model bacterial system which may have application in our understanding of similar processes in higher cells.